NEW YORK — Exactly 10 years ago, ground zero was a smoking, fire-spitting tomb, a ghastly pile of rubble and human remains. On Monday it was a place of serenity — an expanse of trees and water in the middle of a bustling city — as the 9/11 memorial opened to the public.

As they walked through a grove of oaks and traced their fingers over the names of the nearly 3,000 dead, visitors were deeply moved by the monument, whose centerpiece is two sunken pools ringed by bronze plaques.

"When we walked in, those images were popping in my head from 10 years ago," said Laura Pajar of Las Vegas. "But when I saw the memorial, all of that went away. This is so peaceful, and you kind of forget about what happened and you look toward the future."

About 7,000 people registered online for free tickets to visit on opening day, and 400,000 are signed up for the coming months, according to the nonprofit organization that oversees the memorial.

Many visitors made pencil-and-paper rubbings of the names to take back home. Others sat on benches or clustered for photos. Some people cried; others embraced. Some left flowers or stuffed messages into the letters.

"There were no words," Eileen Cristina of Lititz, Pa., said as she wiped away tears. "The enormity of the loss, the enormity of human kindness, the enormity of the suffering."

Families first
The site was opened on Sunday — the 10th anniversary of the Sept. 11 attacks — to the 9/11 families. Monday marked the first day since the tragedy that ground zero was opened to the public.

Security was airport-tight, with visitors forced to empty their pockets, go through a metal detector and send their bags through an X-ray machine.

The memorial takes visitors on a kind of journey. First they walk through a forest of more than 200 white oak trees. Then, like hikers coming upon a canyon, they arrive at two 30-foot-deep pits on the exact spots where the World Trade Center's twin towers stood. Water cascades into the two voids, evoking the dust cloud that accompanied the towers' fall.

The falling water creates a constant whooshing, muffling the noise of the city and nearby construction.

"It's like an entrance to eternity," said Wojtek Ballzun, a rail worker from Warsaw, Poland.

Jim Drzewiecki, a firefighter from Lancaster, N.Y., said he was trembling as he stood next to the pools.

"I'm actually still shaking," he said. "It could have been me on that flight. On any one of the flights. ... There's not much that separates us."

Inspired by mourners
The bronze plates carry the names of the 2,977 people killed in the terrorist attacks in New York, at the Pentagon and in Pennsylvania, plus the names of the six who died in the bombing of the trade center in 1993. The letters have been cut all the way through the metal, with empty space beneath them.

Nearby are a half-dozen electronic directories to help visitors find names, which are grouped not alphabetically but in ways that showed the connections between co-workers, firefighters, airplane flight crews and other victims.

The memorial's architect, Michael Arad, said the plaza next to the pools was inspired by gatherings of mourners that he saw in New York's Washington Square and Union Square after the attacks.

"These places don't just bring us together physically in one spot, they brought us together emotionally," Arad said. "We've recreated that opportunity for that to happen here."

There is a separate entrance for 9/11 family members and comrades of the fallen firefighters and police officers. Certain days or hours will be set aside for them to visit privately.

Workers are still building the 9/11 museum underneath the memorial. It is scheduled to open in 2012 and will include two of the forklike supports that were left standing when the World Trade Center fell, as well as a stairway that enabled hundreds to escape.

Nation's tallest skyscraper
Construction also continues next door on 1 World Trade Center, which is more than 80 stories high so far and will be the nation's tallest building at 1,776 feet.

It is one of several striking new buildings that will eventually surround the memorial. Two World Trade Center will be 1,349 feet high with a diamond-shaped tip and an 80-foot antenna. The 53 stories of 3 World Trade Center will feature crisscross external braces.

Admission to the memorial is free, but visitors must obtain passes in advance that allow them to enter at a specified time.

The cost of the memorial and museum has been put at about $700 million. The nonprofit organization that runs the project has raised about $400 million in private donations and is seeking federal funds.

Jim Brown lost his brother-in-law, Kevin Bracken, and two other relatives on 9/11. He said he felt cheered after seeing Bracken's name permanently on the memorial.

"They never found Kevin," Brown said. "To me his spirit is all over here. ... His spirit will always be here in this part of Manhattan."

Chris Hawley in New York contributed to this report.

Copyright 2011 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Video: 9/11 Memorial opens to the public

Closed captioning of: 9/11 Memorial opens to the public

>>>now that
september 11th
is behind us, along with the tenth anniversary and the tension of the
terror alert
is loosening, new york mayor
michael bloomberg
is asking that we turn a page. he's requesting that people no longer call it
ground zero
, for a lot of reasons and prefers the
world trade center
and the national
september 11th
memorial and museum. the facility actually opened to the public today by appointment. so people got to see for themselves, in person today, just what a powerful place it is. our report tonight from nbc's raheema ellis in
lower manhattan
.

>> reporter: the design called reflecting absence includes two enormous pools in the footprint of the
twin towers
, each about an acre in size with 30-foot cascading waterfalls. the names of all the victims killed in the terror attacked are inscribed into bronze panels surrounding the pools. for many it's turned the site into a heartfelt touchstone.

>>i saw my brother's name. it really just was so powerful for me.

>> reporter: the memorial evokes tears and sadness, but some say it also gives them a feeling of peace.

>>it's quiet. you cannot hear the outside noise coming in from the city. and what you hear most is just the falling water.

>> reporter: the architect intentionally left
space between
the etched names so people could leave something behind for their loved ones. maria's son alex worked on the 90th floor.

>>i left a note and how much we love him.

>> reporter: people also spent time at the site
making memories
of victims' names. jason lost his cousin
neil david levin
who worked for the
port authority
.

>>it's a way to get something tangible out of the site, bring him home with us.

>> reporter: florida firefighter lieutenant orlando siguera was inspired to seek out
robert david
peraz's name after seeing the image of his father in the newspaper today. you found him at the memorial.

>>we did.

>> reporter: what was it like?

>>13 big men started crying. it's emotional.

>> reporter: emotional with so many lives cut short. now a memorial to remember them forever. nbc

Joe Caristo of Miami, who once worked at the World Trade Center, stands silently Sunday, Sept. 11, during a ceremony in New York marking the 10th anniversary of the 9/11 attacks on the World Trade Center. Caristo says he lost friends in the 2001 attacks on the twin towers.
(Craig Ruttle / AP)
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Cho Sok Wells, accompanied by his wife Cathy, kisses their 10-month-old son Cristian while visiting his sister's memorial bench after the 10th anniversary 9/11 ceremony at the Pentagon in Arlington, Va., on Sunday.
(Shawn Thew / EPA)
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Visitors embrace in front of the Wall of Names near the crash site of Flight 93 in Shanksville, Pa., on Sunday.
(Amy Sancetta / AP)
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U.S. flight medic Sfc David Bibb of Santa Fe, N.M., holds an American flag on top of a helicopter Sunday to commemorate the 10th anniversary of the 9/11 attacks at Forward Operating Base Edi in Afghanistan's Helmand province.
(Rafiq Maqbool / AP)
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People gather during a ceremony marking the 10th anniversary of the attacks on the World Trade Center Sunday, Sept. 11, 2011, outside the World Trade Center site in New York.
(Oded Balilty / AP)
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A young man holds his head as he sits in front of a memorial for FDNY firefighters from Ladder Company 20 who died at the World Trade Center on 9/1. New York City firefighters are commemorating the 10th anniversary of the 9/11 terrorist attacks and honoring the 343 firefighters who died in the line of duty.
(Justin Sullivan / Getty Images)
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People observe a moment of silence during ceremonies at the World Trade Center site for the 10th anniversary of the terrorist attacks on lower Manhattan on September 11, 2001 in New York City.
(Spencer Platt / Getty Images)
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Christoffer Molsins, a soldier from Denmark who is being deployed to Afghanistan, holds his dog tags while standing with thousands of others on Church Street in lower Manhattan as they listen to the ceremony marking the 10th anniversary of the 9/11 attacks on the World Trade Center in New York, Sept. 11, 2011.
(Mike Segar / Reuters)
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Helen Jordan of London reads ribbons of remembrance on a fence at St. Pauls Church in Lower Manhattan during events marking the 10th anniversary of the 9/11 attacks on the World Trade Center in New York, Sept. 11, 2011.
(Mike Segar / Reuters)
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Fire fighters and other first responders receive applause as they wind their way through the seats at Parkview Field baseball stadium in Fort Wayne, Ind., Sept 11, 2011. The 9/11 Stair Climb memorial walk started at 8:46 a.m., the time the first plane hit the north tower of the World Trade Center. About 400 people attended the event.
(Samuel Hoffman / The Journal Gazette via AP)
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Mourners embrace during tenth anniversary ceremonies at the site of the World Trade Center in New York, Sept. 11, 2011.
(Lucas Jackson / Reuters)
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Robert Peraza, who lost his son Robert David Peraza in the attacks at the World Trade Center, pauses on Sunday, Sept. 11, at his son's name at the North Pool of the 9/11 Memorial before the 10th anniversary ceremony.
(Justin Lane / Pool via AP)
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Family members arrive Sunday at the check-in area before the ceremonies marking the 10th anniversary of the 9/11 attacks on the World Trade Center in New York.
(Shannon Stapleton / Reuters)
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President Barack Obama, right; first lady Michelle Obama; former President George W. Bush; and former first lady Laura Bush look out at the North Pool of the 9/11 memorial.
(Timothy A. Clary / Pool via Getty Images)
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New York City police and firefighters and Port Authority police officers salute during the singing of the "Star Spangled Banner" at the Sept. 11 memorial, during the 10th anniversary ceremonies at the site on Sunday.
(Chip Somodevilla / Pool via AP)
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A man walks among nearly 3,000 flags set up as part of a remembrance in St. Louis, Mo., on the 10th anniversary of the Sept. 11 terrorist attacks.
(Jeff Roberson / AP)
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People arrive Sunday for the ceremony marking the 10th anniversary of the Sept. 11 terrorist attacks on the World Trade Center.
(Oded Balilty / AP)
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Three small stones are placed over a name on one of the plaques in the '9/11 Memorial' outside Jerusalem on Sept. 11, 2011, during a 10th anniversary memorial ceremony marking the 9/11 terror attacks in the United States, which killed nearly 3,000 people, including five Israelis. It is customary at Jewish cemeteries to place stones on the graves of loved ones. The memorial here contains a large American flag made of bronze that appears to be billowing in the wind, and has plaques containing all of the nearly 3,000 names of the victims, the only site to do so outside the one at the World Trade Center in New York City.
(Jim Hollander / EPA)
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Peace activists release white doves during a commemoration of the 10th anniversary of the 9-11 terror attacks in Berlin, Germany, on September 11, 2011.
(Sean Gallup / Getty Images)
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Members of Clerkenwell Fire Station's Green Watch observe a minute of silence in London, England, on Sunday, remembering their fellow firefighters who lost their lives in the 9/11 terrorist attacks in New York.
(Peter MacDiarmid / Getty Images)
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High school students pose for a photo by a damaged replica of the Statue of Liberty in Ishinomaki, Japan, Sunday. As the world commemorated the 10th anniversary of the World Trade Center attacks, Sunday was doubly significant for Japan. It marked six months since the massive earthquake and tsunami on March 11.
(Hiro Komae / AP)
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Family and friends of those aboard Flight 93 gather on Saturday, Sept. 10, 2011, at the boulder that marks the crash site outside Shanksville, Pa. They were there the day before the 10th anniversary of the terrorist attacks after the dedication of the first phase of the permanent Flight 93 National Memorial.
(Gene J. Puskar / AP)
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Vice President Joe Biden speaks during the dedication of the Flight 93 memorial in Shanksville, Pa.. A long white stone wall bearing the names of those who struggled with al-Qaida terrorists on the fourth airliner to be hijacked on Sept. 11, 2001, was unveiled on the rural Pennsylvania field where the Boeing 757 crashed.
(Nicholas Kamm / AFP - Getty Images)
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Former Presidents George W. Bush and Bill Clinton and former first lady Laura Bush bow their heads during ceremonies in Shanksville, Pa.
(Jason Cohn / Reuters)
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A family member of one of the victims of the crash of United Flight 93 walks along a part of the Flight 93 National Memorial following its dedication. The names of the 40 victims of the crash are inscribed on the marble panels.
(Amy Sancetta / AP)
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Workers take off their hard hats off during the playing of the National Anthem after unfurling a flag on One World Trade Center overlooking the national Sept. 11 memorial on Sept. 10.
(Matt Rourke / AP)
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A tribute to Sept. 11 is seen at Bryant Park on Sept. 10 in New York. There are 2,753 empty chairs -- one for each life lost in New York during the Sept. 11, 2001 attacks.
(Don Emmert / AFP - Getty Images)
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Flags are carried into St. Patrick's Cathedral in New York during a ceremony Sept. 10 to honor New York firefighters killed in the attacks.
(Seth Wenig / Reuters)
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A New York firefighter listens as the daughter of a firefighter who died on Sept. 11, 2001, speaks during the first repsponders' memorial service at St. Patrick's Cathedral in New York.
(Brian Snyder / AFP - Getty Images)
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A visitor takes pictures of flags erected at Battery Park in Manhattan, on Sept. 10 as a part of a project called "One Flag One Life" to marking the 10th anniversary of the attacks.
(Mladen Antonov / AFP - Getty Images)
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A woman writes a message on the wall of remembrance memorial near the World Trade Center in New York on Sept. 10.
(Don Emmert / AFP - Getty Images)
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In Liberty State Park in Jersey City, N.J., on Sept. 10, a man looks at names on the wall of the newly opened Empty Sky memorial to victims of the 9/11 attacks on the World Trade Center. The memorial consists of two 30-foot-tall concrete and steel structures, inscribed with the names of the 746 people from New Jersey who died in the attacks.
(Gary Hershorn / Reuters)
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Dr. Madeline Borquist of Carmel Valley, Calif., uses charcoal to outline the name of her niece, Alison Marie Wildman, during the memorial dedication of the Empty Sky memorial at Liberty State Park on Sept. 10 in Jersey City, N.J. Wildman was killed in the terrorist attacks.
(Andrew Burton / Getty Images)
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Angela Calos, left, and Heather Benedetto visit the National 9/11 Pentagon Memorial on Sept. 10 in Washington. The memorial commemorates the 184 people who died at the Pentagon and on American Airlines Flight 77.
(Brendan Hoffman / Getty Images)
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President Barack Obama hugs a visitor during a visit to Arlington National Cemetery in Washington on Sept. 10.
(Joshua Roberts / Reuters)
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Judy and Bob Poore place a flag at Kennesaw Mountain National Battlefield Park in Georgia on Sept. 10 to help commemorate the 10th anniversary and remember their friend Ann Ransom, one of nearly 3,000 people who died in the attacks. A flag was placed on the battlefield for each victim; the flags will remain flying through Sept. 16.
(David Tulis / AP)
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Editor's note:
This image contains graphic content that some viewers may find disturbing.